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By P. D. I. Honeyman

Changing trends in concentration, involving regrinding with the subsequent production of a finely divided, high-grade flotation product, presents a real problem to the modern copper smelter. In the treatment of such a material, handling difficulties are numerous and potential possible losses may be very great. In many plants, of course, preliminary roasting of the furnace charge remains an economical necessity. Under such circumstances, the operator has no alternative except to follow orthodox roaster reverberatory practice, though taking all possible precautions to avoid excessive dust losses and bad working conditions. In other plants, roasting is not only unnecessary but would be highly undesirable, and at best the charge would be merely dried before entering the reverberatory furnace. In the latter case the possibilities of raw charging loom large. The Miami plant of the International Smelting Co. handles the entire output of concentrates of the several mining companies operating in the Globe-Miami district. All of these companies produce a flotation concentrate which, at the Miami Copper Co. particularly, is all reground and is high in grade. In addition, the Inspiration Copper Co. ships a substantial tonnage of high-grade cement copper to the smelter from its leaching plant. Following the flow sheet of the original plant, all such material received was bedded, dried in Wedge furnaces and smelted in reverberatory furnaces. At times during the history of the plant it has been necessary to carry the drying operation further, to a partial roast, before reverberatory smelting. Since the charge contained over 80 per cent flotation concentrates, the handling of which in a dried condition was at best a dusty job, unusual precautions were taken to cut down dust losses. The Wedge furnace plant was equipped with a Cottrell treater and all hoppers and calcine cars were carefully designed to cut down dust loss in transferring the so-called calcine from hoppers to car and from car to furnace. In the furnace itself the dusting problem was a severe one. Arch erosion was very rapid and flues and waste-heat boilers rapidly filled up with a partly smelted flue dust.

Jan 1, 1934

By J. King Hoyt

IN both Sweden and England rapid progress is being made in metallurgical development, and the steel industry in both countries is distinctly on the mend. There has been some industrial trouble in Sweden in the iron mines and the wood pulp mills, but at the same time all the steel works have a sufficient stock of pig iron and ore to continue their operations for many months to come. Consequently the strike, unless long protracted, will not affect the output of steel in Sweden. Several of the steel manufacturers in Sweden, most notably Forsbacka and Sandviken, have been very suc-cessful recently in securing large orders, particularly from the continent, for ball-bearing steel, both hollow and solid. Whereas some years ago they ran into-se-rious competition with the German mills, the quality of the steel from these Swedish mills is such that they are now firmly established, and are selling some of the lead-ing manufacturers of bearings on the Continent, as well as automobile manufacturers. The secret of their success seems to lie in a better selection of ores, in more careful control of blast-fur-nace operations and better equipment. Rule of thumb in steel making is taboo, and strict reliance is placed on the laboratory. They are constantly experimenting, and metallurgists and chemists are sent to different countries for study and investigation. In their native ores they have, of course, a unique advantage in pos-sessing iron ores extraordinarily free from phosphorus. At Forsbacka, they are not content with the ordinary chemical analysis of the ingot; but also test the physical properties, as well as make metallographic investiga-tions for slag inclusions, segregations and oxides. In both England and Sweden they watch the nitrogen con-tent of the steel very carefully, a feature which does not appear in the ordinary analysis. In testing carbon, they do not use the color test, but employ an electric .induction device.

Jan 7, 1928

By W. B. Watson

IN the USSR considerable technical improvements have been made in hydraulic methods of mining coal. In New Zealand coal mining by these methods is still comparatively crude. The Russian techniques are closely studied in New Zealand, and this description is based mainly on translations of technical articles. Fundamentally the methods in both countries are the same-chief developments in the USSR are the use of high pressure water jets, capable of winning all but the hardest coal without prior blasting, and hydraulic pipeline transportation where the gradient is unsuitable for flume transport.

Jan 4, 1958

By George C. Fryburg

The oxidation of platinum at high temperatures (above 800°C) is controlled by boundary-layer diffusion, except at the lowest pressures. The rate of oxidation is determined by the rate of diffusion of oxide through the boundary layer away from the platinum. This is in contrast to the situation in tungsten and molybdenum oxidation, where the rate is controlled largely by the diffusion of oxygen through the boundary layer towards the metal. The difference in mechanism is a consequence of the much lower rate of oxidation of platinum. Evidence is presented that supports this mechanism for the oxidation of platinum. SOME years ago we reported1 a study of the oxidation of platinum in ordinary oxygen in the temperature region above 800°C, where the oxide is volatile. All the data available up to that time had been obtained with platinum crucibles or plates heated in tube furnaces. The results were widely variant and highly dependent on the flow rate of gas through the furnace: the faster the gas flow rate, the higher the measured oxidation rate. These results indicated to us2 that reaction equilibrium was being approached in the furnace and that the rate was diffusion limited. To minimize these effects, we employed1 electrically heated ribbons placed in a cooled bulb. We were primarily interested in the low-pressure region, but some experiments were performed at pressures up to 1 atm. We found a peculiar pressure dependency which was explained on the basis that the rate of oxidation was proportional to the pressure at all pressures, but that with increasing pressure an increasing fraction of the volatilizing oxide was back-reflected to the ribbon by the surrounding gas molecules. The oxide molecules are not stable at the temperature of the platinum and are decomposed on impact, the platinum being re-deposited on the specimen. Because of the limitations of space, this explanation was offered summarily without detailed support. Recently, Jaffee and associates3, 4 have suggested that the pressure dependency of our data up to 0.5 torr could be explained on the basis of a Langmuir-type adsorption of molecular oxygen followed by dissociation. Since the correct explanation of the effect of pressure on the oxidation rate is a necessary requirement to the development of the basic mechanism of the oxidation reaction, we felt that the back-reflection theory should be presented in more detail. This is the object of the present paper. RESULTS AND DISCUSSION A typical set of results showing the pressure dependency of the oxidation reaction is presented in Fig. 1, where we have plotted, on logarithmic scales, the rate of oxidation, R, vs the pressure, p. For comparison some results of Krier and Jaffee4 and of Raub and plate5 are also shown. These data were taken at atmospheric pressure using furnaces. The effect of reaction equilibrium within the furnace is apparent from the much smaller values that these observers obtained: Raub and Plate In O2 found a rate of 3.1 µg cm-2 hr-1 compared to our value of

Jan 1, 1965

By E. W. Hart, W. R. Hibbard

The room temperature flow characteristics of a series of Cu-Cr alloys are found to be related to the amount and characteristics of the chromium-rich precipitate. The results are consistent with the theory of Fisher, Hart, and Pry, which considers the trapping to dislocation loops around precipitate particles. THE use of dispersed phases for hardening metals, particularly high temperature alloys, has been practiced for several years. Current theories describing the effects of dispersions on the basis of dislocation theory have been proposed by Mott and Nabarro.l-4 rowan," and Fisher, Hart, and Pry.8 These theories recently have been discussed by Hart,' who pointed out that the experimental data available for comparison with theoretical calculations for overaged alloys are confined to studies by Gensamer, Pearsall, Pellini, and Low,8 Shaw, Sher-by, Starr, and Dorn,9 and some hitherto unpublished data on Cu-Cr alloys which will be described herein. Certain difficulties were associated with the interpretation of the first two studies. Gensamer, Pearsall, Pellini, and Low were concerned principally with interparticle spacing and did not document particle sizes. Shaw, Sherby, Starr, and Dorn included all the data in their report which was necessary for the theoretical evaluation, but their study is subject to some question1" due to difference in prior history of various specimens and due to systematic differences in particle characteristics" which appeared to be associated with differences in the magnification of their microscopic examination. The current study was undertaken to obtain critical data in a manner which avoids some of these limitations. Specimens of eight Cu-Cr alloys remaining from a previous investigation'' were available in the form of 100 mil sheet of the compositions shown in Table I. At 200 mil this material had been previously an- nealed ½ hr at 1000°C, water quenched, and cold rolled 50 pct. Samples were further cold rolled to a thickness of 20 mil for a total reduction of 90 pct. Sheet tensile specimens of standard geometry with a gage length 2½ in. long and 0.20 in. wide were machined from this sheet. These specimens were then annealed in a dried N2-H2 atmosphere for the times and temperatures indicated in Table I. This anneal served two purposes: 1—to obtain a fairly uniform and nearly constant grain size of 0.015 to 0.022 mm average diameter, and 2—to precipitate a fairly uniform, nearly spherical over-aged dispersion of essentially pure chromium. A typical microstructure illustrating the grain size and the uniformity of the dispersion is shown in Fig. 1. A typical dispersion illustrating the range of sizes and shapes of the particles is shown in Fig. 2. The tensile specimens were tested in the Instron equipment described in ref. 11 at room temperature at a strain rate of 0.04 in. per in. per min. Three tests were run on each alloy with sufficient repro-ducibility that a single true stress-true plastic strain curve could be drawn through the three sets of data for each alloy. Typical curves are shown in Fig. 3.

Jan 1, 1956

By William N. Poundstone

What attracts young engineering graduates into the coal industry? What do these young men expect of a career in coal mining? These questions are often asked and debated by mining men throughout the country. In order to present a comprehensive answer to them, an opinion survey was conducted at West Virginia University's School of Mines among the junior and senior classes and part of the sophomore class. The tabulation of the answers showed that the present-day mining engineering student is an older, more mature individual as compared with former years and as compared with other present-day college students. The average age of the country's record-breaking 150,000 college graduates is 24 years. Among this year's mining graduates at West Virginia University, 78% are of this age or older. Over half (54%) of those polled in the survey are married. This is com- pared to 30% as a national figure. Of those married, 38% have one child and over 6% have two children. The entire senior group covered by this survey has averaged almost three years in the armed forces. An article entitled "The Class of '49" in the June issue of Fortune magazine states that this year's class is the oldest, most mature class in history. Our survey indicates that the mining engineering students at West Virginia University are well above the average in this respect.

Jan 1, 1949

By R. L. Skaggs, D. T. Peterson

The effect of carbon in solid solution on the plastic behavior of thorium was studied by measuring the flow stress of Th-C alloys from 4.2" to 573°K and at several strain rates. Carbon was found to strengthen thorium primarily by increasing the thermally activated component of the flow stress. The strengthening due to carbon was directly proportional to the carbon content and decreased rapidly with increasing temperature up to 423" K. The flow stress also increased with increasing strain rate. The strengthening appears to be due to a strong short-range interaction between carbon atoms and dislocations. A yield point was observed in the Th-C alloys which increased with increasing carbon content. JTREVIOUS study of the mechanical properties of thorium has been confined largely to the measurement of the engineering properties. Work prior to 1956 has been summarized by Milko et al.1 who reported that additions of carbon to thorium sharply increased the room-temperature strength. In addition, the yield strength was observed to decrease rapidly over the temperature range from 25" to 500°C. In 1960, Klieven-eit2 measured the flow stress of thorium containing 400 ppm C. He found that over the temperature range from 78" to 470°K the flow stress was strongly dependent on temperature and rate of deformation. A drop in the load-elongation curve, or a yield point, was observed over most of the above temperature range. Above 470°K, the flow stress was nearly independent of temperature and strain rate. This strong temperature and strain rate dependence of flow stress is not generally observed in fcc metals. It is, in fact, more typical of the behavior reported for bcc metals. Bechtold,3 Wessel,4 and conrad5 have pointed out the striking difference between the commonly studied bcc metals and fcc metals in regard to the effect of temperature and strain rate on the flow stress. Zerwekh and scott6 studied the plastic deformation of thorium reported to contain 12 ppm C. They found that this material did not obey the Cottrell-Stokes law as expected for fcc metals. In addition, they found values of the activation volume smaller by an order of magnitude than expected for an fcc metal. They concluded that thorium was strengthened by a randomly dispersed solute. Thorium differs from many other fcc metals that have been studied extensively in that it shows a relatively high carbon solubility at room temperature. Mickleson and peterson7 report the solubility limit at room temperature to be 3500 ppm C. The lowest value reported is that of Smith and Honeycombe8 who report the limit to be 2000 ppm C at 350°C. The pres- ent investigation was a systematic study of the flow stress and yield point phenomenon of thorium over a broad range of carbon content, temperature, and strain rate. EXPERIMENTAL PROCEDURE The thorium used in this investigation was produced by the reduction of thorium tetrachloride with magnesium as described by Peterson et a1.' Chemical analysis of the original ingot after arc melting and electron beam melting is shown in Table I. Alloys were prepared by arc melting this thorium with high-purity spectrographic graphite. Threaded specimens with a gage length 0.252 in. diam by 1.6 in. long were used for the constant stress or creep measurements. These specimens were machined from rod which had been cold-rolled and swaged to % in. diam. Tensile specimens were prepared by swaging annealed 3/8 -in.-diam rod to 0.102 *0.001 in. The as-swaged wire was cut to lengths of 2 in., annealed, and the center 1-in. gage length elec-tropolished to 0.100 ±0.001 in. The specimens were gripped for a length of 3 in. at each end by a serrated four-jaw collet which was tightened by a tapered compression nut. No slipping occurred in the grips and negligible deformation was observed outside the 1-in. gage length. Both the creep and tensile specimens were annealed at 730°C under a vacuum of 1 x X Torr. The resulting structures consisted of equiaxed recrystallized grains with a grain size of 3200 grains per sq mm for the tensile specimens and 2200 grains per sq mm for the creep specimens. After the specimens were prepared, samples were analyzed for nitrogen, oxygen, and hydrogen. The results of these analyses are given in Table 11.

Jan 1, 1969

By B. D. Cullity, J. T. Norton, M. Telkes

THIS investigation of antimony-selenium alloys was undertaken in an attempt to find a suitable material for use in power-generating thermocouples. The chief requirements for such a material are high thermoelectric power, low electrical resistivity and low thermal conductivity. Measurements of the first two properties mentioned are usually sufficient to determine whether or not a material is suitable for use in a thermoelectric generator. As a first approximation the requirements are: 1. Thermoelectric power greater than 200 microvolts per °C. 2. Electrical resistivity less than 0.002 ohm-cm. 3. Thermal conductivity less than 0.015 watt per cm per "C. These quantities are averages for the Operating temperature range. Previous Work Experimental investigations of equilibrium in the antimony - selenium system have been summarized by Han-sen². These investigations extended from 1906 to 1921. In Hansen's judgment, the most accurate phase diagram is that determined by Parravano, in 1913 and this is reproduced in the upper part of fig. 1. The most notable parts of this diagram are the liquid miscilibility gap, extending from about 12 to 36 wt pct selenium, and the intermediate phase Sb2Se3 containing 49.3 wt pct selenium. The crystal structure of Sb2Se3 has not been determined. Pelabon3,4 made measurements of the electrical resistivity of a few antimony-selenium alloys but his investigation was not very complete. He found that the resistivity increased with the selenium content and became very large as the composition of Sb2Se3 was approached. For alloys containing less than 50 at. pct (39.3 wt pet) selenium, he found that the resistivity increased regularly with temperature. For alloys containing larger amounts of selenium, he found various results: in some cases, the resistivity decreased with increas-

Jan 1, 1951

By W. C. Shanks

Seventeen deeps, which contain hot or cold brines and/or metalliferous sediments, have been discovered in the axial rift zone of the Red Sea. Metalliferous activity results from the unique geological setting of this incipient ocean basin: oceanic crust intruding in a central rift zone flanked by thick evaporite sequences. Brine pools tend to occur in structural depressions where- transform faults intersect the spreading axis. The most significant metalliferous occurrence is in the Atlantis II Deep, which contains approximately 227 Mt (dry weight) of metalliferous sediment which averages 1.04% Zn and 0.28% Cu. Higher potentially economic grades (3-6% Zn, 1% Cu, 50 glt Ag) occur in the Southwest Basin of the Atlantis II Deep, comprising total metal tonnages of 1.7 Mt Zn, 0.4 Mt Cu, and 5000 t Ag. The Pre-Pilot Mining Test conducted in 1979 raised 15 000 m3 of mud by a slurry process and demonstrated the feasibility of mining, concentration by froth flotation, and tailings disposal at sea. A Pilot Mining Test is scheduled for 1983-1984. The metalliferous discoveries in the Red Sea provide a model example of deep marine mineral exploration. Detailed mapping of bottom bathymetry and brine-interface reflectors using a high-resolution narrow-beam echo sounder has been the most effective exploration tool in the Red Sea. Followup coring has discovered additional metalliferous deposits in basins without present-day brines, and potential exists for additional discoveries. Geochemical exploration using heavy metals values in sediments (iron, manganese, zinc, copper, and mercury) and sulfur isotope values of sulfides are considered to be the most promising techniques for discovery of currently inactive deposits. Positive sulfur isotope values in the range I to 17 are an indication of hydrothermal sulfides in the Red Sea, and there is considerable contrast from back- ground bacteriogenic sulfides ( - 10 to - 45).

Jan 1, 1983

By Joseph Hodgson

Introduction SINCE about 70 per cent. of the total cost of mining is due to underground work which is out of sight, it is essential that expenditures should be made here to the best advantage. A great many mistakes have been made which were expensive, but perhaps these have not even been detected by mine owners. In the future these may be minimized to some extent, especially if there is cooperative effort on the part of each employee. I have been interested in this subject for some years and have tried to deduce principles and methods. These have proved highly advantageous and may also be of help to others. Some corporations, like the United States Steel, and the Cleveland-Cliffs Iron Co., have done a great deal in this field by having stated meetings of their organizations, with the view to interchanging ideas among their men and educating them along the lines of concerted effort. Since no man knows all about the various branches of mining, it is advisable that frequent meetings of the operating department be held for the interchange of ideas and that all members of the organization have an opportunity to express themselves on the various subjects. It has often been found that in discussions between heads of departments, foremen and bosses, many valuable suggestions may be obtained which promote the best interests of the company. The method regarded as the most conducive to cooperative effort, and pursued by the organization, is to analyze and develope the different phases of various mining subjects at regular meetings.

Jan 5, 1916

Discussion of the paper of W. C. PHALEN, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 93, September, 1914, pp. 2249 to 2265. DAVID T. DAY, Washington, D. C.-Consider the United States broadly and the distribution of the salt industry. Think of the old solar-evaporation process up in New York State, then of the more recent processes in Michigan and Kansas and Louisiana, where the rock salt furnishes a large industry, then of the solar-evaporation process at Salt Lake, then turn to the crucial place in the United States, where there is an embarrassment of salt, and that is California. I am not forgetting' the immense body of salt east of that in the Virgin River country of Utah; but in California the situation is interesting. There are very large quantities of salt in the Searles Marsh region; again, in Southern California, at the southern end of Death Valley, there are two or three mountains of salt which have been explored recently, where the salt is sufficiently pure to be used at once. There is also a large deposit of gypsum, and it would be possible there, by extremely cheap means, to produce an amount of salt sufficient to furnish the United States' greatest needs. The principal reason that capital has been deterred from developing such a large mass is not the fact that solar evaporation produces a great deal of salt around San Francisco, but the fact that if potash salt is to be produced in connection with the salt in the borax region a, great deal of ordinary salt must be disposed of. It cannot be dumped, for it would get back into the brine again; the first rains would bring that salt back into solution again. It must be sold, given away, or hauled to a distance, which would mean a considerable freight charge. The salt will be going begging. E. G. SPILSBURY, New York, N. Y.-The remark of Dr. Day's regarding the likelihood of the production of a large amount of waste salt brings to my mind the condition that obtains in Germany in all of the potash fields. In Germany salt is a government monopoly. In the development of the potash deposits, it becomes a grave question as to how much salt they may be allowed to extract and bring to the surface.

Jan 4, 1915

By Joe O. Ledbetter

INTRODUCTION Health physics as a profession really got a significant start during the Manhattan Project of World War 11. The Health Physics Society has recently published its 25th anniversary issue of the journal (June 1980). There was concern over radiation exposures during and after uranium production, especially about radium and its daughter products [Jackson 19401 and, as evidenced by the frequency of articles in the literature, there still is. The reason for this concern was expressed by Harley as "Workers engaged in the mining and pro- cessing of radium-bearing materials are exposed to dusts of the parent, to radon, and to the radon daughter products. In- haled radioactive particulates may be retained in the lung or redistributed to other organs of the body. Relatively minute de- posits of radioactive substances, particularly alpha emitters, have been clearly shown to be the etiological factor in a variety of injuries to industrial and re- search workers. " [Harley 1953] Emphasis in measurements has been placed on radium in water and radon in air, since these are the principal mobilized phases; however, it should be kept in mind that radium-containing particles do become suspended in air as aerosols and radon absorbs in liquids. Much of the uranium mining and production is being carried out aboveground. The principal difference between underground and surface (pit or leach) mining of uranium is the reversal in the relative importance of roles for the types of radiation dose. For aboveground the major radiation exposure is external gamma ray, whereas for underground it is internal alpha; for aboveground, the whole body penetrating is of greater importance than the lung alpha dose. AS a result of the politics involved and the law- suits for any and all diseases as being occupationally- caused, today , more than ever before, the successful performance of the activities connected with uranium production--before-, during-, and after-the-fact-- must include the provision of first class radiation protection. Such protection can be achieved by good measurements, thorough risk evaluations, and adequate controls. Meeting the ALARA (As Low As Reasonably Achievable) philosophy necessarily entails the determination of what is reasonable exposure. The necessary and sufficient elements of radiation safety under the ALARA dictum require a hard look at the dose versus effects data. There are times when the health physicist needs to make decisions of judgement rather than compliance with a well-defined regulation value. In order to facilitate such decisions, the real world must be separated from opinions that are merely artifacts of statistical variation and from the unprovable "what ifs" that are slanted to question the morality of any non-Luddite. UNITS VOCABULARY FOR DOSIMETRY There have been many radiation quantifying and dosimetric units introduced in the past. Fortunately, most of them did not catch on enough to become required knowledge for reading the health physics literature. The unit definitions necessary for our purposes here are the following: -curie (Ci)--unit of radioactivity equal to 3.7 x 10 10 disintegrations per second Webster&apos;s 19711 or the quantity of radionuclide that undergoes 3.7 x 10 nuclear transformations per second. Environmental levels of radioactivity are usually measured in picocuries (10-l2 Ci) per cubic meter for air and in picocuries per liter (pCi/~) for water and sometimes for air. .roentgen (R)--exposure dose of x or gamma rays that gives 1 esu of charge (either sign) to 1 cc of dry air @ STP. The roentgen is equivalent to an energy absorption of 86.7 ergs/g of air [Gloyna and Ledbetter 19691. .rad--radiation absorbed dose of 100 ergs per gram of absorber. The SI unit for absorbed radiation dose is the Gray; 1 Gy = 100 rads. orem--radiation absorbed dose of 1 rad times the quality factor (QF) for that radiation. The QF is 1 for x rays, gamma rays, beta rays, and posi- trons. For heavy ionizing particulate radiation, QF is a function of the amount of energy trans- ferred per unit length of travel, i.e. , the linear energy transfer (LET); the values of QF:LET in keV/um are as follows: 1:<3.5; 1-2:3.5-7; 2-5:7-23; 5-10:23-53; and 10-20:53-175 [Morgan and Turner 19 671 . For radiobiology, relative biological effectiveness (RBE) is recommended for use instead of the quality factor above that is for radiation protection: the RBE is the ratio of the dose of 200 kVp x rays to the dose of radia- tion in question (both in rads) to cause the same

Jan 1, 1980

By Lawrence Adler

The authors are to be complimented on using a novel and potentially helpful technique to analyze the effects of mine roof trusses. However, some criticisms of their application and analysis seem appropriate to further its acceptance. This discussion will deal with the normal structural analysis format covering: 1) material, 2) load, 3) structure, and 4) analysis. It will then briefly review the testing procedures and finally cover miscellaneous items.

Jan 12, 1978

By C. Chu

An investigation has been made of the radial heat-wave process using a mathematical model in two-dimensional cylindrical coordinates. This model considers combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. From a study of the general features of the process, an important phenomenon has been revealed, namely, the feedback of heat into the reservoir on the trailing edge of the heat wave. The effects of various process variables on the performance characteristics of the process have also been investigated. It was found that up to the time when the combustion front reaches a given point, the per cent heat loss, provided it is not higher than 40 per cent, is approximately directly proportional to the square root of thermal conductivity arid fuel content, but inversely proportional to the square root of gas-injection rate and oxygen concentration. The effecr of reservoir thickness is more pronounced, since halving the thickness doubles the per cent heat loss. The most decisive factor in determining the center-plane peak temperature is the fuel content of the reservoir. Within the temperature range investigated, doubling the fuel content doubles the peak temperature in the early stage, but the rate of decline of the peak temperature is high. Reservoir thickness is also a very influential factor. The peak temperature is lowered when the thickness is reduced; however, the effect of thickness becomes less pronounced when the thickness is high. Reduction of oxygen concentration increases the peak temperature in the early stage but lowers it afterwards because of the higher rate of decline of the peak temperature. Increase in gas injection rate or decredse in thermal conductivity geives a higher peak temperature which stays high for a longer period. The propagation range of the heat wave is chiefly governed by the fuel content of the reservoir. An increase of 0.2 1b/cu ft in the fuel content increases the propagation range by 100 per cent. The propagation range is more than doubled by doubling the gas injection rate, or reservoir thickness, or by reducing the thermal conductivity by 50 per cent. Comparatively, oxygen concentration has less effect on the propagation range. INTRODUCTION Several investigators have conducted theoretical studies of a radial heat wave. Vogel and Krueger1 studied a system with a moving cylindrical heat source of constant temper- ature, considering conduction in the radial direction only. Ramey2 included conduction in the vertical direction in his studies. Bailey and Larkin2 attacked a more general problem where initial well heating, vertical heat losses and arbitrary frontal velocities were included. In all these studies, however, conduction was considered to be the only means of heat transfer. Bailey and Larkin in a later paper included the effects of convection in a study involving both linear and radial geometries. Vertical heat losses were neglected in the radial case. Katz5 studied a similar problem in a one-dimensional radial model, using a heat-loss coefficient to account for vertical heat losses. Selig and Couch6 mployed a cylindrical model and investigated two limiting cases. In one case they considered no heat loss from the reservoir whereas in the other they assumed a constant temperature at the interface between the reservoir and its bounding formations. Thomas&apos; studied a more general case but assumed a permeable bounding formation so that the convection effect is not confined to the reservoir. In the present work a more realistic and more generalized model is used. It involves a two-dimensional cylindrical system with combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. The purpose is to establish the temperature distribution both inside and outside the reservoir, to study the general features of the radial heat wave process, and to investigate the effects of various process variables on the performance characteristics of the process. THEORY We fist consider a circular porous reservoir of thickness H extending vertically from y = — H/2 to y = + H/2. The reservoir extends from a well bore radius r, to an external radius re. A stream of oxygen-containing gas is introduced into the reservoir through the wellbore. The oxygen-containing gas reacts with the fuel contained in the reservoir and forms a combustion front wherever the prevailing temperature can support the combustion. It is here assumed that this combustion front constitutes a cylindrical surface source of heat having an infinitesimal thickness in the radial direction and extending vertically throughout the whole thickness H. This is designated as Region I. We next consider a Region II corresponding to the upper and lower formations bounding the reservoir, extending from y = — - to y = — H/2 and from y = + H/2 to y = + m. Since r, is very small, we may assume that the two bounding formations have the same dimensions, symmetric with respect to the center plane of the reservoir. In this way, we may take the upper half of the system alone into consideration. In contrast with

By J. E. Campbell, A. W. Wesner, M. Pobereskin

This paper summarizes the results of an investigation sponsored by The Coates Steel Products Company. The objective was to determine the relative effects of certain chemical and physical properties on the wear resistance of grinding balls when grinding cement. In making this study, a number of types of balls were used in both dry and wet grinding in commercial ball mills. The radioactive-tracer technique was used in separating the test balls from the rest of the mill charge and in sorting the different types of halls that were all tested at the same time for each of the grinding operations. PROCESSING OF GRINDING BALLS In order to determine whether the properties of grinding balls, namely, composition, microstructure and hardness, can be related to the rate of wear, the halls used in this study were selected to represent various combinations of these properties. It was recognized that the mechanism of wear was not the same in the wet mill as in the dry mill. Therefore, the types of balls tested in each of the two environments were not necessarily the same. However, all of the types of balls evaluated in the dry mill were tested simultaneously for one time period, while those evaluated in the wet mill were tested simultaneously for three different time periods. All of the test balls were separated from the charge when the mill was dumped. All of the balls were of 0.940-inch diameter when charged, and all but the regular production balls were finish ground to this size to eliminate the decarburized surface layers. The steels and processing methods used, as well as the micro-structures and hardness levels of the balls, are described as follows: Regular production forged SAE 1095 steel balls were used in both the wet and dry mills. They were forged to a nominal diameter of 0.940 inch and quenched in oil from the forging temperature. Each retained a partially decarburized surface layer from the forging bar stock; the maximum depth of this layer was about 0.030 inch and the decarburization was negligible where the ball was sheared from the bar. The hardness at the surface was 40 to 46 Rock-well C in the partially decarburized area and 57 to 62 Rockwell C in the areas not decarburized. The hardened zone extended to a depth of about one-third of the radius. Below the decarburized layer, the hardened zone consisted primarily of hard as-quenched martensite with varying amounts of retained austenite. This structure changed to fine pearlite at a depth of about one-third of the radius. In order to eliminate the effect of the decarburized layer, a set of production balls of SAE 1095 steel was forged to about a 1-inch diameter, quenched in oil from the forging temperature, and ground on ball-bearing grinding equipment to a 0.940-inch diameter to remove the decarburized layer. The balls&apos; hardened zones were similar to those in the previous set. The hardness of the finished surfaces was 52 to 60 Rockwell C. A slight amount of decarburization apparently remained after the removal of about 0.030 inch from the surface. Balls of this type were tested in the dry mill only. Another set of forged SAE 1095 steel balls of 1-inch diameter was heated to 1500 F and quenched

Jan 1, 1961

While the production of this state has not realized the early hopes that this coal would replace eastern coal on the Pacific Coast, it has been steady though small. Nearly all of the tonnages given are from Goodyear&apos;s, The Coal Mines of the Western Coast of the U. s., a carefully com- piled and accurate account of the development of the industry along the Pacific. [ ]

Jan 1, 1942

By d&apos, John C. Entremont

Pure iron was inductively melted in small refractory crucibles and optical pyrometer and immersion thermocouple readings were simultmzeously taken. The resulting emissivities of the liquid iron surface obtained were found to be greatly affected by both the gaseous atmosphere and geometrical changes in the physical setup. Quantitative values for these effects are indicated. FOR many applications in both the laboratory and plant, optical pyrometry is still the best means of measuring temperatures in the incandescent range. A prerequisite in evaluating the correct temperature is a good value of the emissivity of the surface. To obtain the emissivity from the tabulated values of the literature can be very confusing and often far from correct. There are many reasons for these difficulties, and it is not within the scope of this paper either to enumerate or to discuss them all. Its purpose is to show quantitatively how several factors affect the apparent emissivities obtained from experimental measurements on liquid iron surfaces. The black body is the reference state for the quantitative values of emissivities and is defined1 as a body which absorbs all radiation incident on it, reflecting none; such a surface emits more radiation per unit area per unit time than any surface which reflects any radiation, and is given a value of unit emissivity. All bodies having reflective power thus have emissivities less than unity and are considered nonblack or grey bodies. The ratio of the radiant energy emitted by the flat, nonblack surface to that of a perfectly black surface of equal area and temperature is the emissivity of the surface. The above definitions are applied to flat, polished, opaque surfaces, very seldom encountered in actual measurements, and for this reason many authors have suggested that the word "emittance" be used for real bodies rather than emissivity. The emittance has reference to the material and its configuration rather than to its properties in the idealized state. Recent observations of molten iron in a small refractory crucible indicate that not only the configuration of its surface but the geometrical arrangement of its surrounding and the nature of the surrounding atmosphere have a pronounced effect on the emittance. Neglect of changes in such conditions may lead to errors as large as 40°C at 1600°C. Thus it is suggested that the term "apparent emissivity" be used and that it be recognized that its value pertains to a particular experimental arrangement only. As a result of not recognizing these differences in emissivities, which are obtainable from changes in the physical setup of an observation, many investigators have incorrectly quoted their values as those of the emissivities of particular materials rather than as an apparent emissivity for their particular arrangements. As a consequence, values of the emissivity of liquid iron ranging from 0.3 up to 0.55 are found in the literature. In an effort to establish an accurate optical temperature scale for liquid iron solutions in which de-oxidation studies were to be carried out, it was observed that the temperature relationship, obtained by simultaneously taking immersion thermocouple

Jan 1, 1963

By T. A. Rickard

Do not write until you have something to say. Think first; then write. In order to be understood, you must know what you wish to say. Clear writing is the consequence of clear thinking. Therefore consider your subject well before you begin to write; ruminate on it; marshal the salient facts in your mind; saturate yourself with the ideas you wish to express and with cognate ideas; then express yourself deliberately. If you are bubbling over with your subject the words will come, but you might as well expect to sail without a breeze as hope to give life to words without the living thought. Here I may advert to the fact that among the uneducated it is a common expectation to acquire the knack of writing without taking the trouble to study the art of literature. I overheard a woman in a suburban train remark to her neighbor: "I&apos;d like to be able to write well without stopping to think about it". She was one of many that would like to do a thing well without the trouble of thinking; but it cannot be done in respect of anything to which thought is essential. The possession of a good voice does not justify a person in expecting to sing successfully to a large audience; before singing in public one has to master the technique of singing; one has to learn first how to breathe properly, how to enunciate, and many other things. The successful singer is an artist, not a megaphone. Most of us would regard a man or a woman without any training in the art of singing as a fool or an impostor if he or she were to give a public concert, yet we do not recognize the equal foolishness and imposture of persons that write books before they have studied the technique of writing. That is why so many books are unreadable, and why many books by clever men are difficult to read. They start to write books before

Jan 1, 1931

By Leon Merker

FLAME fusion growth of strontium titanate crystals was undertaken to obtain large transparent crystals on which physical data could be gathered. The fact that strontium titanate is a cubic crystal and probably has a high index of refraction indicated that it might be useful in optics. No large boules* of strontium titanate had been synthesized previously, and none have been found as natural occurrences. The flame fusion process, invented by Verneuil in 1904,1 was first applied to grow large crystals of ruby and has since been used extensively to grow crystals of corundum and spinel on a commercial scale. Only during the past nine years has this technique been applied to the growth of large single crystals of other high melting compounds such as rutile,2 mullite,3 and ferrites4 One of several significant advantages of the flame fusion technique over more conventional methods of growing crystals from a melt is that the crystals are grown without the use of melt containers. This fact alone excludes other methods of growing crystals from a melt whenever there are compounds with a melting point near 2000°C or above. Growth of the crystal, similar to that of a stalagmite, takes place inside a circular refractory furnace that does not contact the crystal, Fig. 1. This eliminates a serious source of impurities as well as the likelihood of multi-crystalline solidification along the container walls. The flame fusion technique is particularly advantageous for research because it produces large crystals quickly and at lower cost. A corundum crystal 25 mm long and 12 mm in diam can be grown in 2 to 3 hr. Operating conditions permit observation of the growing crystal during any stage of the process. The various flame patterns and a wide range of oxidation-reduction conditions can be investigated in a relatively short time. It should be pointed out that formation of the foot of the boule is the most critical step in growing an unfractured boule. When the tip of the sintered cone is fused to initiate crystal growth, the original area of fusion should be kept as small as possible so that one crystallite can assume dominance over all the others and propagate as a single crystal. If the boule start happens to consist of several crystals, usually the entire boule also contains several crystals. In many cases these tightly cohering crystals exhibit different crystallographic orientations. Although the basic technique of the original Verneuil process has been retained, refinements in method and burner design have been developed in recent years. For example, boule growth may be initiated on a seed crystal rather than by fusion of a sintered cone. The danger of multicrystalline or twinned boule starts is thus eliminated, and this procedure may also be used to grow boules of predetermined crystallographic orientation. Prior Art: Of the many attempts to produce artificial gem crystals, most early efforts% ere directed toward synthesis of .rubies and sapphires and diamonds. None of these efforts resulted in a process that was commercially practical. Without exception only tiny crystals of corundum were obtained, and those at excessive cost. Verneuil announced his process in 1904; Ravier6 in 1934 presented a detailed description of a commercial boule production plant. Descriptions of the German synthetic stone industry, the process details, and the equipment used have been published by Barnes7 and by Merker.&apos;

Jan 1, 1956

By C. S. Barrett

It has been observed that deformation in iron takes place by slip on (110) + {112) + (123) planesl, 2, but in silicon ferrite with low deformation temperatures or high silicon contents (exceeding 4 per cent) the authors have found that slip is confined wholly to (110) planes, at least with small amounts of deformation. The purpose of the present investigation was to determine the effect of this alteration of slip mechanism on preferred orientations in cold-rolled and recrystallized strips. Incidental observations on the effect of the recrystallization temperature were also made. The numerous determinations of the texture of cold-rolled iron and steel have been in satisfactory agreement as to the principal features of the texture (with the exception of a few conclusions that apparently have been based on insufficient data). The texture is chiefly one in which 11101 directions of the grains lie along the direction of rolling, with a deviation of a few degrees, and in which the (100) planes lie in the plane of the rolled sheet, with a deviation from this position chiefly about the rolling direction as an axis. This deviation about the rolling direction as an axis has been measured by different observers and lies between about 45" and 50" or 60" for iron5, 6, 9 and is usually in the neighborhood of 50" for mild stee16, 7, 8. The range of this deviation is a function of the percentage of total reduction8, 10. Post8 reported that it decreases with increasing percentage reduction, but apparently he studied only the surface material, which Gensamer and Meh17 found to be somewhat differently oriented from the material in the inside of the sheet. McLachlan and Davey10 found that the deviation also decreases with increasing percentage of total reduction for the material in the interior of the sheet and is independent of the percentage of reduction per pass. The deviation about the cross direction as an axis (the direction in the

Jan 1, 1937